logo
    Abstract:
    Star formation in massive galaxies is quenched at some point during hierarchical mass assembly. To understand where and when the quenching processes takes place, we study the evolution of the total star formation rate per unit total halo mass (\Sigma(SFR/M)) in three different mass scales: low mass halos (field galaxies), groups, and clusters, up to a redshift ~1.6. We use deep far-infrared PACS data at 100 and 160 um to accurately estimate the total star formation rate of the Luminous Infrared Galaxy population of 9 clusters with mass ~10^{15} M_{\odot}, and 9 groups/poor clusters with mass ~ 5 x 10^{13} M_{\odot}. Estimates of the field \Sigma(SFR/M) are derived from the literature, by dividing the star formation rate density by the mean comoving matter density of the universe. The field \Sigma(SFR/M) increases with redshift up to z~1 and it is constant thereafter. The evolution of the \Sigma(SFR/M)-z relation in galaxy systems is much faster than in the field. Up to redshift z~0.2, the field has a higher \Sigma(SFR/M) than galaxy groups and galaxy clusters. At higher redshifts, galaxy groups and the field have similar \Sigma(SFR/M), while massive clusters have significantly lower \Sigma(SFR/M) than both groups and the field. There is a hint of a reversal of the SFR activity vs. environment at z~1.6, where the group \Sigma(SFR/M) lies above the field \Sigma(SFR/M)-z relation. We discuss possible interpretations of our results in terms of the processes of downsizing, and star-formation quenching.
    Keywords:
    Stellar mass
    Field galaxy
    In this Thesis we analyse in detail the Anglo-Australian 2 degree Field Galaxy Redshift Survey (2dFGRS). The goal of this survey is to measure all galaxy redshifts for the 250 000 galaxies brighter than b(_J) = 19.45 spread over ~ 2000 square degrees. At present, the 2dFGRS has obtained redshifts for ~ 190 000 galaxies. It is currently the biggest galaxy redshift survey in existence and represents an order of magnitude increase in size over any previous survey. The study of the large-scale structure of the Universe is undergoing a revolution due to important technological advances in observational astronomy that make surveys like the 2dFGRS possible. This new era in mapping the Universe demands the development of new theoretical analysis tools, both to exploit the large amounts of data, and to take advantage of, for the first time in cosmology, the extraordinary opportunity to push random errors below the level of the systematic errors. By a detailed analysis of the survey construction and observing strategy, we implement a set of maps to estimate, as precisely as possible, the selection function of the 2dFGRS. These maps, which characterize the survey completeness, enable us to estimate accurately fundamental properties of a homogeneous galaxy sample: the galaxy luminosity function and real space galaxy clustering. By combining the 2dFGRS with the near infra-red 2MASS survey, we estimate the K(_s)-band galaxy luminosity function, from which we infer the stellar mass function of galaxies. This yields a total mass fraction in stars between 0.1% and 0.3% of the critical cosmic density. Exploiting the size of the survey, we undertake the first precise measurement of the dependence of galaxy clustering on luminosity and spectral type. Star-forming galaxies as well as more quiescent galaxies show a clear increase in clustering strength with luminosity at a similar rate. This is the first time that we are able to examine in detail the properties of galaxies that drive their spatial distribution.
    Field galaxy
    Redshift-space distortions
    Citations (0)
    Fundamental to our understanding of the universe is the evolution of structures, from galaxies to clusters of galaxies to large-scale sheets and filaments of galaxies and voids. The investigation of the evolution of large-scale structure not only provides us with the key test of theories of structure formation, but also allows us to measure fundamental cosmological parameters. The CNOC2 (Canadian Network for Observational Cosmology) Field Galaxy Redshift Survey is the first large redshift survey of faint galaxies carried out with the explicit goal of investigating the evolution of large scale structure. This survey also provides the largest redshift and photometric data set currently available for the study of galaxy population and evolution at the moderate redshift range between 0.1 and 0.6. In this paper we describe the scope and technique of the survey, its status, and some preliminary results.
    Field galaxy
    Citations (2)
    We describe and apply a simple prescription for defining connected structures in galaxy redshift surveys. The method is based upon two passes with a friends-of-friends groupfinder. The first pass uses a cylindrical linking volume to find galaxy groups and clusters, in order to suppress the line-of-sight smearing introduced by the large random velocities of galaxies within these deep potential wells. The second pass, performed with a spherical linking volume, identifies the connected components. This algorithm has been applied to the 2dFGRS, within which it picks out a total of 7,603 systems containing at least two galaxies and having a mean redshift less than 0.12. Connected systems with many members appear filamentary in nature, and the algorithm recovers two particularly large filaments within the 2dFGRS. For comparison, the algorithm is has also been applied to LambdaCDM mock galaxy surveys. While the model population of such systems is broadly similar to that in the 2dFGRS, it does not generally contain such extremely large structures.
    Field galaxy
    Line-of-sight
    Degree (music)
    We study galaxy correlations from samples extracted from the 2dFGRS final release. Statistical properties are characterized by studying the nearest neighbor probability density, the conditional density and the reduced two-point correlation function. The result is that the conditional density has a power-law behavior in redshift space described by an exponent ± 0.2 in the interval from about 1 Mpc/h, the average distance between nearest galaxies, up to about 40 Mpc/h, corresponding to radius of the largest sphere contained in the samples. These results are consistent with other studies of the conditional density and are useful to clarify the subtle role of finite-size effects on the determination of the two-point correlation function in redshift and real space.
    Field galaxy
    Degree (music)
    Exponent
    Citations (18)
    We extend the Fourier transform based method for the analysis of galaxy redshift surveys of Feldman, Kaiser & Peacock (FKP) to model luminosity-dependent clustering. In a magnitude-limited survey, galaxies at high redshift are more luminous on average than galaxies at low redshift. Galaxy clustering is observed to increase with luminosity, so the inferred density field is effectively multiplied by an increasing function of radius. This has the potential to distort the shape of the recovered power spectrum. In this paper, we present an extension of the FKP analysis method to incorporate this effect, and present revised optimal weights to maximize the precision of such an analysis. The method is tested and its accuracy is assessed using mock catalogues of the 2-degree field galaxy redshift survey (2dFGRS). We also show that the systematic effect caused by ignoring luminosity-dependent bias was negligible for the initial analysis of the 2dFGRS of Percival et al. However, future surveys, sensitive to larger scales, or covering a wider range of galaxy luminosities, will benefit from this refined method.
    Field galaxy
    We determine the low-redshift field galaxy stellar mass function (GSMF) using an area of 143 deg^2 from the first three years of the Galaxy And Mass Assembly (GAMA) survey. The magnitude limits of this redshift survey are r < 19.4 mag over two thirds and 19.8 mag over one third of the area. The GSMF is determined from a sample of 5210 galaxies using a density-corrected maximum volume method. This efficiently overcomes the issue of fluctuations in the number density versus redshift. With H_0 = 70, the GSMF is well described between 10^8 and 10^11.5 Msun using a double Schechter function with mass^* = 10^10.66 Msun, phi_1^* = 3.96 x 10^-3 Mpc^-3, alpha_1 = -0.35, phi_2^* = 0.79 x 10^-3 Mpc^-3 and alpha_2 = -1.47. This result is more robust to uncertainties in the flow-model corrected redshifts than from the shallower Sloan Digital Sky Survey main sample (r < 17.8 mag). The upturn in the GSMF is also seen directly in the i-band and K-band galaxy luminosity functions. Accurately measuring the GSMF below 10^8 Msun is possible within the GAMA survey volume but as expected requires deeper imaging data to address the contribution from low surface-brightness galaxies.
    Stellar mass
    Field galaxy
    Surface brightness fluctuation
    Luminosity functions and their integrated luminosity densities are presented for the 6-degree Field Galaxy Survey (6dFGS). This ongoing survey ultimately aims to measure around 150 000 redshifts and 15 000 peculiar velocities over almost the entire southern sky at |b| > 10°. The main target samples are taken from the 2-Micron All-Sky Survey (2MASS) Extended Source Catalog and the SuperCOSMOS Sky Survey catalogue, and comprise 138 226 galaxies complete to (K, H, J, rF, bJ) = (12.75, 13.00, 13.75, 15.60, 16.75). These samples are comparable in size to the optically selected Sloan Digital Sky Survey and 2-degree Field Galaxy Redshift Survey (2dFGRS) samples, and improve on recent near-infrared-selected redshift surveys by more than an order of magnitude in both number and sky coverage. The partial samples used in this paper contain a little over half of the total sample in each band and are ∼90 per cent complete.
    Field galaxy
    In This paper the cluster analysis technique (The Euclidean Separation Distance Coefficients) is used to test the membership of individuals in groups of galaxies and apply specific criteria to identify the members which should be excluded from these groups. The method is applied to quintet galaxy groups taken from final release of the two degree field galaxy redshift survey (2dFGRS) . The sample included 4739 quintets with total number of 23695 galaxies. The final results indicate that 317 Groups have one galaxy that has attribute discordant and should be discarded from its grou p.
    Field galaxy
    The construction of a catalogue of galaxy groups from the 2-degree Field Galaxy Redshift Survey (2dFGRS) is described. Groups are identified by means of a friends-of-friends percolation algorithm which has been thoroughly tested on mock versions of the 2dFGRS generated from cosmological N-body simulations. The tests suggest that the algorithm groups all galaxies that it should be grouping, with an additional 40% of interlopers. About 55% of the ~190000 galaxies considered are placed into groups containing at least two members of which ~29000 are found. Of these, ~7000 contain at least four galaxies, and these groups have a median redshift of 0.11 and a median velocity dispersion of 260km/s. This 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue represents the largest available homogeneous sample of galaxy groups. It is publicly available on the WWW.
    Field galaxy
    Velocity dispersion